The current invention relates to the field of downhole drilling, including horizontal drilling, oil and gas drilling, geothermal drilling, dry hot rock drilling, mining, and exploratory drilling. In downhole drilling applications, several different methods and bits for impacting or drilling into rock formations have typically been used. Among these methods are rotary or shear drill bits, percussion bits, and roller cone bits. There are also drill bits which use both shearing and percussive forces for drilling. Some inventions of the prior art also have methods for centering a drill bit or for reducing bit whirl while drilling.
U.S Pub. No. 2002/0166700 by Gillis et al., which is herein incorporated by reference for all that it contains, discloses an apparatus for introducing a consistent series of small and localized rotary impacts to a PDC bit during drilling to improve PDC drill bit performance. Rotary impact supplements the nominal torque supplied by the rotary drive thereby avoiding lockup and potentially damaging energy storage in the drill string following windup, should the bit slow or hang up when drilling in difficult formations. The apparatus comprises a rotary hammer which is rotated about a bit shaft's anvil, preferably by a drilling fluid driven turbine. As the hammer rotates, potential energy is built up. When the hammer and anvil connect, the energy is released into the bit shaft and thus into the bit, increases its instantaneous torque and allows it to more effectively cut through difficult formations.
U.S. Pat. No. 6,948,560 by Marsh, which is herein incorporated by reference for all that it contains, discloses a jar for use in a downhole toolstring comprising: a hollow housing; a jar mandrel; a latch sub; one or more latch keys; a cam surface; a chamber; a compression spring; and an adjuster.
U.S. Pat. No. 6,877,569 by Koskimaki, which is herein incorporated by reference for all that it contains, discloses a method for controlling the operating cycle of an impact device, and an impact device. Percussion piston position is measured using a sensor from which the measurement data is transmitted to a control unit of the impact device, which in turn controls an electrically driven control valve.
U.S. Pat. No. 6,745,836 by Taylor, which is herein incorporated by reference for all that it contains, discloses a self-contained radial drive unit that is driven by a linear input, which can be supplied from various source. As linear motion is applied to the input of the tool, drive pins on a drive shaft follow a helical path, converting the linear motion into radial motion at the attached mandrel end.